In carpentry, drafting, and other mechanical arts, the need often arises to mark a surface at regular intervals. For example, in placing siding, setting tile, or installing framing members, the need to calculate and mark precise locations at specific intervals repeatedly arises. The conventional approach to marking involves employing a conventional ruler or tape measure with the user performing mental calculations to determine where each mark should be placed. This method is time consuming and frequently leads to error. In turn, marking error can lead to drafting error, calculating error, or error in construction. For instance, in many engineering disciplines including civil and mechanical engineering and architecture, the spacing of structural elements such as frames, beams, or columns is linked to the calculation of stiffness or weight carrying capability of the structure. If, in drawing the structure to be built or in laying out framing at the site, errors occur in positioning the structural members, serious consequences for structural adequacy to withstand the applied forces may result. The ability to calculate and mark standard intervals quickly and with confidence thus provides an important advantage to the engineer, draftsman, or worker assembling the structure. Despite the drawbacks, marking of increments is typically accomplished with nothing more sophisticated than a ruler or tape measure.
Mechanical markers and dividers are well known in the art. So called "lazy-tong" or scissor-joint dividers such as the device disclosed in patent Ser. No. 381,560, operate by dividing a specific length-wise measurement into a selected number of equally spaced intervals. These devices allow the user to select the total length and the number of sections into which it will be divided. When the user mechanically opens or closes a plurality of interlocking folding dividers, the device indicates where the marks are to be placed. Alternatively, devices such as these may be used to indicate a plurality of equal intervals, each having a particular dimension. Indeed, some devices, including those disclosed by patent Ser. No. 425,168, patent Ser. No. 736,168, patent Ser. No. 877,795, U.S. Pat. No. 1,643,968, U.S. Pat. No. 3,157,953, and U.S. Pat. No. 3,250,014 include a ruled plate to assist the user in determining the measurement of the interval being marked.
There are many disadvantages of the lazy-tong or scissor-joint types of devices. These tools are usually awkward and heavy. They also require the device to be manipulated physically to achieve the desired interval. Moreover, when these devices are constructed of metallic parts, they can mark or mar delicate surfaces such as paper, plastic, or fine wood, if great care is not exercised while using them.
Where use of these devices involves physical manipulation of a plurality of hinges, a great deal of force may be required. The tool may become rusted, corroded, or bent such that accurate positioning by the user becomes impeded, physically difficult, or time consuming. Furthermore, to the extent that the device is large, heavy or awkward, it becomes difficult for the user to hold the device in a particular orientation while transferring incremental marks to the surface being marked. A related problem with some lazy-tong or scissor-joint dividers is that the device may slide out of position while the marks are in the process of being transferred. If detected, correction of the error requires the user to recalibrate and re-mark the increments. Alternatively, if undetected, sliding occurring during the marking process may result in the transfer of erroneous markings, with subsequent errors in construction.
Other tools such as the device disclosed in U.S. Pat. No. 4,212,108, which do not rely on a lazy-tong or scissor-joint type of design, tend to be relatively inflexible in allowing selection of intervals. Some tools are limited to a single application, such as determining the spacing of studs used to frame a wall or applying siding, and are not easily adapted to other uses.
One further drawback of all the aforementioned devices is that they are not ideal for use in low light conditions. When the task of marking is, for example, being performed inside a house under construction or outside on an overcast day or near dawn or twilight, an illuminated device would add to the user's confidence in placing marks in the correct locations.
Accordingly, an object of this invention is to make an incremental measuring device which is both accurate and reliable and also easy to handle and use. Another object of this invention is to produce a tool that is useful in a variety of applications and disciplines. Another object of this invention is to provide a durable, lightweight tool. Another object of this invention is to provide a tool that is rugged enough for heavy use, but compatible for use in delicate tasks such as drafting. Still another object of this invention is to provide a device that does not have a large number of moving parts that may become frozen, rusted, or otherwise difficult to manipulate or that may shift inadvertently during the marking operation. Yet another object of this invention is to provide a device with illuminated indicators that may be seen easily in low or uncertain lighting conditions.